Bolster spring unit



c. J. CHRISTENSON 2,551,204

' BOLSTER SPRING UNIT Filed Sept. 30, 1947 Jive/17w" 61,455.7 (W/"zbZEnJOL/ Patented May 1, 1951 UNITED STATES PATENT OFFICE 3 Claims.

This invention relates to improvements in bol-, ster spring units and it consists of the matters hereinafter described and more particularly pointed out in the appended claims.

One of the objects of the present invention is to provide a simple and efficient unit for supporting bolsters of railroad cars that include novel means that functions instantly to frictionally resist the compression of the unit under load and its rebound or expansion upon release of load.

Another object of the invention is to provide a unit of this kind having its parts so arranged as to function equally as well in lightly loaded cars as in heavier loaded ones.

A further object of the invention is to provide a unit of this kind embodying a minimum number of parts that are easy to assemble and which requires no center bolt to hold the parts together in assembled relation.

Also it is an object of the invention to provide a unit of this kind, which may be disposed in position, with either end up, thus eliminating danger of error in assembly in a spring group between the bolster and spring plank of a truck frame.

The above mentioned objects of the invention, as well as others together with the advantages thereof will more fully appear as the specification proceeds.

In the drawing:

Fig. 1 is a view in side elevation of a railway car truck in which the improved bolster spring unit is shown in position thereon.

Fig. 2 is a longitudinal vertical sectional view through the improved bolster spring unit on a scale enlarged over that of Fig. 1.

Fig. 3 is a horizontal sectional view through the improved unit as taken on the line 33 of Fig. 2.

Fig. 4 is a View in elevation showing the inside of one of a plurality of friction shoes embodied in the improved unit.

Fig. 5 is a vertical sectional view through the shoe appearing in Fig. 4, as taken on the line 55 thereof.

Fig. 6 is a diagrammatic flat development view showing the interengagement between the friction shoes of the two sets of such shoes embodied in the unit, and permitting a limited relative longitudinal guided movement therebetween.

Referring now in detail to that embodiment of the invention illustrated in the drawings HI indicates as a whole the side frame of a railway car truck and i l indicates the supporting wheels therefor. The side frame has the usual columns I2 between which the end of a bolster I3 is arranged to slide with a vertically guided movement. Below said bolster is located a conventional spring plank l4 and interposed between said bolster and spring plank is a nest of load supporting springs 15, only one of which appears in Fig. 1, and at least one of the improved bolster spring units, which is indicated as a whole by the numeral It. The number of load supporting springs in each set may vary, depending upon the character of the truck.

The improved unit embodies a load supporting helical spring ll of relatively heavy square crosssectional stock and takes the form of a compressible and expandable cylinder.

In each end of the spring I! is located a set of shoes 18, one of which best appears in Figs. 4 and 5, each set consisting of a pair of such shoes, all of said shoes being counterparts. Each shoe has a semicylindrical head 19 at one end and a body 20 about 90 in circumferential extent and said head and body have an outer peripheral cylindrical frictional surface 2| of the same diameter, for engagement with the inner cylindrical surface of the spring l'l. Each shoe has a length somewhat greater than one-half the length of the spring l1, when the same is not under load, and on the inside of the head and extending partway into the body of each shoe is a tapered wedging surface 22, which best appears in Figs. 4 and 5. At the end of each body is a pair of laterally extending lugs 23.

When the sets of such shoes are in assembled position, the body 25 of each shoe in one set is disposed between the bodies of the two shoes of the other set and the lugs 23 of the shoes of one set are opposed to the lugs of the shoes in the other set, so that they prevent separation of the shoes of both sets longitudinally of the unit. This interengaged disposition of the shoes is best illustrated in the fiat development in Fig. 6.

When the sets of shoes are assembled together within the spring ll, they function as a sectional cylinder, with the shoes capable of a relative longitudinal and lateral movement. Within said sets of shoes is located a helical wedging spring 24 fitting within the space afforded by the bodies of the sets of shoes with some lateral clearance. The spring 24 is a helical open wound spring and the end convolutions are more closely wound and restricted in diameter toward the end extremities thereof to form tapered wedging surfaces 25. These surfaces normally engage the surfaces 22 of the shoes of both sets and tend to urge the sets of shoes longitudinally as well as laterally outwardly so as to frictionally engage the inside surface of the load supporting spring IT. The action of the spring 24 is such as to frictionally hold the shoes in engagement with the spring l1 and therefore the unit is maintained for handling in an assembled condition Without the aid of a center bolt. Further, as the structure of the unit is the same at each end, either end may be disposed to face upwardly and therefore it is not possible to assembly the unit among the nest of supporting springs i5 of the car truck in any but the proper manner.

It is to be noted that the ends of the shoes are flush with the ends of the main load supporting spring. Thus the unit will start its snubbing action promptly either under light or heavy loads and therefore the unit is sensitive in operation.

When the unit is under load, such as will compress the load carrying spring H, the shoes of both sets of shoes will move relatively longitudinally toward each other. This will cause the spring 24 to apply greater force to the shoes l8, thereby pressing the surfaces 2| more tightly into frictional snubbing engagement with the inside of the load supporting spring I1. Upon release of load the spring 24 expands and continues to press said surfaces 2! into snubbing engagement with the spring l7. Thus the unit functions as well in lightly loaded cars as when heavily loaded.

By reason of the lugs 23 on the shoes, said shoes cannot become separated by longitudinal movement and therefore after assembly, no center bolt is required to hold the parts together in assembled relation. Also the unit consists of but the minimum number of parts, in this instance six, so that it is simple and easy to produce and assemble.

While in describing the invention I have referred in detail to the form, construction and arrangement of the parts involved, the same is to be considered only in the illustrative sense and therefore I do not wish to be limited thereto except as may be specifically set forth in the appended claims.

I claim as my invention:

1. A bolster spring unit embodying therein a main load supporting spring, a set of friction shoes within each end of said spring and having external cylindrical surfaces for frictional engagement with the internal cylindrical surface of said spring, the shoes of one set being relatively movable longitudinally with respect to the shoes in the other set and the shoes in each set being relatively movable laterally, means providing internal wedging surfaces on the shoes of each set thereof, and spring means acting at its ends against the wedging surfaces of the shoes of both sets thereof for forcing the same laterally to engage their cylindrical surfaces with the coacting surface of the spring.

2. A bolster spring unit embodying therein a main load supporting spring, a set of friction shoes within each end of said spring and having external cylindrical surfaces for frictional en gagement with the internal cylindrical surface of said spring, each shoe including a head and a body and having cylindrical surfaces for frictional engagement with the internal surface of said spring, the bodies of the shoes of one set interfitting between the bodies of the shoes of the other set so that said bodies are relatively longitudinally movable with a guiding action therebetween, means providing internal wedging surfaces on the shoes of each set thereof, and spring means acting at its ends against the wedging surfaces of the shoes of both sets thereof for forcing the same laterally to engage their cylindrical surfaces with the internal surface of the spring.

3. A bolster spring unit embodying therein a main cylindrical load supporting spring, a set of friction shoes within and associated with each end of said spring and having exterior cylindrical surfaces for frictional engagement with the internal surface of said springs, the shoes of one set being relatively movable longitudinally with respect to the shoes of the other set, said shoes being formed at opposite ends of the unit with internal inwardly flaring wedging surfaces, and a spring Within said sets of shoes and having tapered end portions that are complemental to and are constantly engaged with the wedging surfaces of said sets of shoes for forcing the same outwardly to operatively engage their external friction surfaces with the internal friction surfaces of said load supporting spring.

GUST J. CHRISTENSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,127,658 McCormick Feb. 9, 1915 1,616,411 Canfield Feb. 1, 1927 1,956,671 Dentler May 1, 1934 1,988,295 Berry Jan. 15, 1.935 2,097,523 Hedgcock et al. Nov. 2, 1937 2,395,171 Dath Feb. 19, 1946 2,470,172 Leese May 17, 1949 

